1. Field of the Invention
This invention relates to technology on communication between processors in a multi-processor system.
2. Prior Art
In some cases, controllers for controlling automobiles may adopt a multi-processor system for improvement of their processing ability. Judging from improvement of cost performance, a conventional multi-processor system has a plurality of processors which are connected each other by their built-in serial communication interfaces (SCI: Serial Communication Interface). The transmission speed of the SCI is about 500K to 1M bits per second (maximum) depending upon kinds of processors.
In the meantime, a communication interface for peripheral units (SPI: Serial Peripheral Interface) has been well known as a faster serial communication interface than the SCI. The SPI can transfer data at about 4M to 10M bits per second (maximum) depending upon kinds of processors. However, this interface is a single master type full duplex bi-directional communication interface for peripheral units and can let only one transmission-starting master exist on the serial line.
For example, Japanese Application Patent Laid-Open Publication No. Hei 09-293047 discloses an SPI system which uses SCI and SPI cables to connect microcomputers and external devices which monitors memory data of the microcomputers. In this system, the external units use the SCI cables to send high-order addresses of memory data to the microcomputers. The external units use the SPI cables to send low-order addresses of memory data to the microcomputers and to receive memory data from the microcomputers.